Air circuit breaker



R E. FRINK ET AL Sept. 6, 1955 AIR CIRCUIT BREAKER 4 Sheets-Sheet 1Filed April 18, 1952 Fig. l.

n O H G U S n 3 INVENTORS Russeii E. Fvink and Paui Oisson.

o AMM AT ORNE YV WiTNESSES:

R. E. FRINK ET AL AIR CIRCUIT BREAKER Sept. 6, 1955 4 Sheets-Sheet 2Filed April 18, 1952 Fig. 3.

QNVENTORS Russell E. Frink and Paul Qisson. QJ Aim;

A u ATTORNEQ WITNESSES: 21x2 4 Sepia 1955 F2. E. FRENK ET AL AIR CIRCUITBREAKER 4 Sheets-Sheet I5 Filed April 18 Frink and WETNESSES: gi a 44mSept. 6, 1955 R. E. FRINK ET AL AIR CIRCUIT BREAKER 4 Sheets-Sheet 4Filed April 18, 1952 INVENTORS Russell E. Frink and Paul Olsson. a BYl/Z ATTORNE F lg 7 WITNESSES: 94 I. W.

United States Patent AIR CIRCUIT BREAKER Russell E. Frink and PaulOlsson, Pittsburgh, Pa., .as-

signors to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application April 18, 1952, Serial No.283,038

8 Claims. (Cl. 200-144) This invention relates to circuit breakers and,more particularly, to contact structures for air circuit breakers.

An object of the invention is to provide a circuit breaker with animproved contact structure which fits into a relatively small space andhas high current-carrying capacity.

Another object of the invention is to provide a circuit breaker with animproved contact structure having high interrupting and current-carryingcapacities Which is rugged and durable in construction.

Another object of the invention is to provide a circuit breaker with animproved contact arrangement according to the preceding paragraphswherein the magnetic forces induced by the current flow are utilized toincrease the contact pressure.

Other objects and advantages of the invention will be pointed out in thefollowing description and illustrated in the accompanying drawings,which disclose, by way of example, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

In said drawings:

Figure l is a side elevational view, partly in section, of r a circuitbreaker embodying the principles of the invention;

Fig. 2 is a detail view of the latch mechanism;

Fig. 3 is an enlarged side elevational view, partly in section, showingthe improved contact structure in the closedcontact position;

Fig. 4 is an enlarged elevational View of the stationary contactstructure taken along line IV-IV of Fig. 3 and looking in the directionof the arrows;

Fig. 5 is a bottom view, partly in section, of the stationary contactstructure shown in Fig. 4;

Fig. 6 is a vertical sectional view of the contact structure taken online VI-VI of Fig. 4, showing the contacts in full lines in the closedposition, and in dot-and-dash lines in the position at which the maincontacts are about to separate; and

Fig. 7 is a view similar to Fig. 6 but showing the contacts in fulllines in the position at which the intermediate contacts are about toseparate and in dot-and-dash lines in the position at which the arcingcontacts are about to separate.

Referring to Fig. 1 of the drawings, the circuit breaker is of theroll-out type and is mounted on a truck comprising a pair of side plates11 (only one being shown) which are rigidly joined by cross members 13,15, 17, and 19 to form a rigid frame for supporting the circuit breaker.The truck is mounted on wheels 20 to facilitate rolling the breaker intoand out of a cubicle in order to connect and disconnect the breaker inan electrical circuit.

The circuit breaker is of the multi-pole type (only one pole beingshown) and comprises generally a plurality of sets of separable contactmeans 21, a common operating mechanism 23, a trip device 25, and aclosing means 27.

The contact means consists generally of stationary contact blocks 29 and31 mounted respectively on upper and lower terminal members 33 and 35which, in turn, are

rigidly supported on a back plate 37. The back plate 37- is rigidlysupported by angular brackets 39 (only one being shown) rigidly securedto the side plates 11 of the frame. The detailed description of theimproved contact structure will be fully described hereinafter.

The specific structures of the operating mechanism, trip mechanism andthe closing means shown are fully disclosed in Patent No. 2,515,994,issued July 18, 1950, to Joseph D. Findley, Alvin W. Ogg, and Fritz E.Florschutz and assigned to the assignee of the instant invention, forwhich reason only a brief description of these mechanisms is givenherein.

A switch arm 41 for operating the movable contacts (there being a switcharm 41 for each pole of the breaker) is pivotally mounted by a pivot pin43 on the lower terminal member 35 and is operatively connected by meansof an insulating operating rod 51 to the operating mechanism 23. Theupper ends of the operating rods 51 are pivotally connected by pivotpins 53 to the corresponding switch arms 41, and the lower ends of theoperating rods are connected by suitable means to an angular crossbar 59which is common to all of the poles of the breaker. The crossbar 59 ispivotally connected at its ends by pivot pins 55 (only one being shown)to an operating lever 61 which is pivotally mounted on a shaft 67supported in the side members of a generally U-shaped frame 69. Theframe 69 is supported on the cross members 13, 15, and 17 and is shownpartly broken away more clearly to show the operating mechanism.

In addition to the operating lever 61, the operating mechanism consistsof a closing lever also mounted on the shaft 67 and connected by meansof a link 81 to the movable armature 85 of the closing solenoid 27 Theoperating lever 61 and the closing lever 75 are connected by means of anunderset thrust-transmitting toggle comprising toggle links 87 and 89pivotally connected together by a knee pivot pin 91. The toggle link 87is pivotally connected to the operating lever 61 and the toggle link 89is pivotally connected to the closing lever 75.

The closing lever 75 is held in the closed position by a spring-biasedlatch which normally engages a roller 101 on the closing lever and holdsthe latter in the position shown.

The toggle 87-89 is releasably held in a slightly underset position by alatch member 103 mounted on the shaft 67 for movement relative thereto.A link 105 connects the knee of the toggle 87-89 to the latch member 103which is normally releasably held in latching position by the latchingand tripping mechanism shown in Fig. 2. This mechanism comprises a tripmember 109 carrying a latch roller 119 which is biased by a spring 123into latching engagement with a shoulder on the latch member 103 toreleasably restrain the latter and the toggle 87-89 inthrust-transmitting position.

The latch 109 is of the slip-off type, and a trigger latch 127 isprovided to releasably restrain the latch member 109 and the latchroller 119 in latching position. The latch 127 has a projection 131normally engaging a latching projection 133 on the trip member 109 andis biased to latching position by a spring 135. A tripping electromagnet137 is provided to operate the latch mechanism and effect release of theoperating mechanism and opening of the circuit breaker.

When an overload current occurs, the tripping electromagnet 137 isenergized and operates the latch mechanism to eifect release of thelatch 109 which, in turn, releases the latch member 103. Upon release ofthe latch member 103, the toggle 87-89 immediately collapses, permittingclockwise rotation of the operating lever 61 and operating movement ofthe switch arms 41 for the several poles of the breaker.

The toggle 87-89 is reset to its thrust-transmitting position, and thelatch member 103 is reset and relatched automatically during the openingoperation. This is effected by a pair of springs 169 (only one beingshown) connected under tension between the armature 85 and the closinglever 75 at a point near the shaft 67. When the toggle 87-89 collapses,a roller 175 on the toggle link 89 engages and moves the latch 95 todisengage the latter from the roller 101, thus releasing the closinglever 75 whereupon the springs 169 move the armature 85 and through thelink 81 rotate the closing lever 75 clockwise. This movement extends thetoggle 8789 to its underset position and through the link 105 rotatesthe latch member 103 clockwise to its latching position, ermittingresetting of the latching mechanism to latching position. Thereafter,the circuit breaker is closed by energization of the closing solenoid 27from any suitable source. When energized, the solenoid 27 attracts itsarmature 85 and through the link 81 rotates the closing lever 75counterclockwise. Since the toggle 87-439 is held in thrust-transmittingposition, the movement of the closing lever is transmitted therethroughand actuates the operating lever 61 and the rods 51 to close the contactmeans 21. As the mechanism reaches the closed position, the latch 95reengages the roller 101 and restrains the breaker mechanism in theclosed circuit position.

Referring now to Fig. 3 of the drawings, the switch arm 41 ischannel-shaped and has rigidly mounted thereon a pair of laterallyspaced main movable contacts 177, an intermediate contact 179 and anarcing contact 181. The main movable contacts 177 cooperate with spacedmain stationary contacts 183. The movable intermediate contacts 179cooperate with a stationary intermediate contact 185, and the movablearcing contact 181 cooperates with a stationary arcing contact 187. Thestationary intermediate contact 185 and the stationary arcing contact187 are mounted on a contact platform 205 (see also Figs. 4, 5, 6, and7) mounted on the upper contact block 29 for limited movement relativethereto by means of a pair of spaced plates 207 disposed one on eachside of the contact block 29. The plates 207 are supported on bolts 209,extending through openings in the contact block 29 and threaded at bothends to receive nuts 210. Springs 212 are compressed between the nuts210 and the plates 207 to provide good contact pressure between theplates 207 and the contact block 29. The plates 207 are provided withelongated slots 214 surrounding the lower bolt 209 to permit limitedpivotal movement of the plates about the upper bolt 209.

The platform 205 is provided with laterally extending studs 211 disposedadjacent the lower end theerof and extending into elongated slots 213 inthe plates 207 for supporting the platform for limited movement relativeto the plates 207. Ears 215 extend laterally from the sides of theplatform 205 into openings 217 in the plates to limit the movement ofthe platform.

The platform 205 is biased outwardly away from the contact block 29 bymeans of a coil spring 219 (Figs. 3, 6, and 7) disposed adjacent theupper end of the platform 205 and a pair of coil springs 221 (Figs. 3 to7) located near the lower end of the platform. The spring 219 iscompressed between the contact block 29 and the contact platform 205 andis provided with a guide stud 223 secured to the contact block 29. Thesprings 221 are compressed between the ends of a U-shaped flexibleconductor 225 (Fig. 3) which serves to electrically connect the contactplatform 205 to the contact block 29. A flexible conductor 227electrically connects the lower end of the switch arm 41 to the lowercontact block 31.

The main stationary contacts 183 are formed on the lower corners of theplates 207 (Figs. 3, 4, and and extend inwardly toward each other. Aconnecting bar 229 is supported on pins 231 mounted in the bar 229 andsupported in openings in the main contacts 183. Springs 233 compressedbetween the bar 229 and a bar 235 secured to the contact block 29 biasthe plates 207 in a clockwise direction about the upper bolt 209 andprovide contact pressure between the main stationary contacts 183 andthe main movable contacts 177 in the closed position of the switch arm41. The purpose of the connecting bar 229 is to tie the plates 207together laterally while permitting a slight independent pivotalmovement of each of the plates.

When the trip device 25 (Fig. 1) is energized and effects collapse ofthe toggle 8789, the operating lever 61 starts to rotate clockwise,permitting downward movement of the rod 51 and movement of the switcharm 41 about its pivot 43 in opening direction. As the switch arm 41moves in opening direction, the stationary contacts 183, and 187 remainin contact, respectively, with the moving contacts 177, 179 and 181until the slot 214 in the plates 207 engages the lower bolt 209, theplates 207 pivoting about the upper bolt 209 by the pressure of thesprings 233. The contact structure is shown in full lines in Fig. 6 inthe closed position and in dot-anddash lines at 214a in the position inwhich the slots 214 have engaged the bolt 209, and the main contacts177-183 are about to separate. In this position the switch arm 41 hasmoved to the position shown at 41a but the contact platform 205 hasfollowed the switch arm under the pressure of springs 219 and 221. Itwill be noticed by reference to Fig. 6 that the slots 213 in the plates207 have moved to the dot-and-dash position 213a and that the studs 211on the platform have moved to the position shown at 211a but are not yetin contact with the left-hand walls of the slots 213. The plates 207 donot move farther during an opening operation, but upon continuedmovement of the switch arm 41 in opening direction, the platform 205follows until the studs 211 engage the left-hand ends of the nowstationary slots 213 in the plates 207. At this time the main contactshave separated slightly as shown at 183a and the intermediate and arcingcontacts are still engaged in the position shown at 185a. The parts areshown in this position in full lines in Fig. 7.

As the opening movement of the switch arm 41 continues, the platform 205pivots about the studs 211 and the upper end thereof follows the switcharm with the arcing contact 187 maintaining contact with the movingarcing contact 181 until the ears 215 are stopped by striking the wallsof the openings 217 in the contact plates 207. In this position of theparts, shown by dot-and-dash lines in Fig. 7, the main and intermediatemovable contacts have opened to the positions shown, respectively, at177b and 179k and the arcing contacts are about to separate.

Upon continued opening movement of the moving switch arm 41 from theposition 4112 (Fig. 7) the arcing contacts separate and the switch armwill move to the open position without further movement of the contactplatform 205 or the contact plates 207, drawing an are between thearcing contacts. The are is drawn into an arc-extinguishing structure,indicated generally 237 (Fig. 1), where it is quickly extinguished.

The contacts close in the reverse sequence when the switch arm 41 isoperated to the closed position, that is, the arcing contacts closefirst, then the intermediate contacts, and finally the main contactsclose.

In the type of circuit breaker illustrated, the arc will usually beextinguished when the arcing contacts have separated approximately twoinches. When interrupting capacitor banks or are furnaces and undercertain conditions when the circuit constants give a low damping factorand the current is of sufficient magnitude, a switching surge may beproduced which will cause the arc to restrike across a gap of thisdimension or larger. Such restrikes may even occur outside the arc chutebetween live or grounded parts such, for instance, as between the mainstationary contacts and the switch arm 41 at a point below the mainmovable contacts. The latter is prevented by providing the switch armwith an insulating sleeve 239.

The contact structure provides increased momentary and continuouscurrent-carrying capacity in a small compact arrangement which permitsplacing the entire separating contact structure inside the arc chute;hence, any restriking of the arc will occur between the interruptingcontact structure and will be confined within the arc extinguisher.

While there has been shown and described and pointed out the novelfeatures of the invention as applied to a single modification, it willbe understood that various omissions and substitutions and changes inthe forms and details of the device illustrated and in its operation maybe made without departing from the spirit of the invention.

We claim as our invention:

1. In a circuit breaker, stationary contacts comprising a fixed contactmember, a pair of spaced movable contact carrying plates disposed one oneach side of said fixed contact member and mounted on said fixed contactmember for limited movement relative thereto, springs providing pressurecontact between said contact carrying plates and said fixed contactmember, main stationary contacts on said movable contact carryingplates, a contact member disposed between said contact carrying platesand supported between said movable contact carrying plates for limitedmovement relative thereto, intermediate and arcing contacts on saidcontact member, and a movable switch member having movable main,intermediate and arcing contacts thereon for cooperating, respectively,with said stationary main, intermediate and arcing contacts to open andclose the circuit.

2. In a circuit breaker, stationary contacts comprising a fixed contactsupport member, a pair of movable c0ntact carrying plates disposed oneon each side of said fixed contact support member and pivotally mountedon said fixed contact support member for limited pivotal movementrelative thereto, a plurality of springs biasing said movable contactcarrying plates into pressure contact with said fixed contact supportmember, main stationary contacts mounted on said movable contactcarrying plates, a contact-carrying member supported between saidmovable contact carrying plates for limited movement relative to saidcontact carrying plates, intermediate and arcing contacts mounted onsaid contact-carrying member, and a movable switch member having movablemain, intermediate and arcing contacts mounted thereon for cooperating,respectively, with said stationary main, intermediate and arcingcontacts to open and close said circuit.

3. In a circuit breaker, a pair of spaced terminals, a stationarycontact structure comprising a conducting member rigidly mounted on oneof said terminals, a pair of movable contact plates pivotally mountedone on each side of said conducting member for limited sliding movementrelative thereto, main stationary contacts rigid with said movablecontact plates, springs biasing said movable contact plates forpivotally moving said main stationary contacts away from said conductingmember, spring means biasing said movable contact plates into pressureengagement with said conducting member, a rigid contact member havingstationary intermediate and arcing contacts thereon, said rigid contactmember being mounted on said movable contact plates and biased forlimited movement relative to said movable contact plates and saidconducting member, and a movable switch member pivotally mounted on theother of said terminals and having movable main, intermediate and arcingcontacts rigid therewith for cooperating with said stationary contactstructure to open and close the circuit.

4. In a circuit breaker, a pair of spaced terminals, a stationarycontact structure supported on one of said terminals comprising a memberof conducting material rigidly secured to one of said terminals, a pairof spaced movable contact-carrying members mounted on said conductingmember, said contact-carrying members being pivotally mounted one oneach side of said conducting member for limited movement relativethereto, main stationary contacts rigidly mounted on said spaced movablecontact-carrying members, said contact-carrying members having openingstherein, a rigid contact member having stationary intermediate andarcing contacts rigid therewith, said rigid contact member havingprojections thereon engaging in said openings in said spaced movablecontact-carrying members to support said rigid contact member forlimited movement relative to said spaced movable contact-carryingmembers, and a switch arm having main, intermediate and arcing contactsthereon and pivotally mounted on the other of said terminals formovement into and out of engagement with said stationary contactstructure to open and close said circuit.

5. In a circuit breaker, a pair of spaced terminals, a stationarycontact assemblage mounted on one of said terminals comprising a pair ofspaced contact-carrying members having openings therein and pivotallymounted one on each side of said terminal for limited movement relativeto said terminal, each of said contact-carrying members being biasedaway from said terminal and having a main stationary contact thereon,spring means biasing said contact-carrying members against oppositesides of said terminal to provide pressure contact therebetween, a rigidcontact member having stationary intermediate and arcing contacts rigidtherewith and having projections thereon engaging in the openings insaid spaced contact-carrying members to support said rigid contactmember for limited movement relative to said spaced contact-carryingmembers, spring means biasing said rigid contact member away from saidterminal, a movable switch arm having a movable contact assemblage rigidtherewith comprising movable main, intermediate and arcing contacts, andsaid movable switch arm being pivotally mounted on the other one of saidterminals and movable to an open position and to a closed position tocause engagement and disengagement of said movable contact assemblagewith said stationary contact assemblage.

6. In a circuit breaker, a pair of spaced terminals, a member ofconducting material mounted on one of said terminals, a pair of spacedcontact-carrying members having a plurality of openings therein anddisposed one on each side of said conducting member, each of saidcontact-carrying members having a main contact rigid therewith, pivotmeans pivotally mounting said contact-carrying members on saidconducting member for movement relative thereto, stop members forlimiting the movement of said contact-carrying members relative to saidconducting member, springs biasing said contact-carrying members intoclose engagement with said conducting member, a rigid contact memberdisposed between said spaced contact-carrying members and havingintermediate and arcing contacts rigid therewith, a plurality ofprojections on said rigid contact member engaging said openings tosupport said rigid contact member between said contact-carrying membersfor movement relative thereto and for limiting said movement, a pivotedswitch arm pivotally supported on the other of said terminals and havingmovable main, intermediate and arcing contacts rigid therewith, saidswitch arm being movable to an open position and to a closed position toeffect engagement and disengagement of said movable contacts with thecorresponding stationary contacts.

7. In a circuit breaker, a pair of spaced terminals, a stationarycontact structure comprising main, intermediate and arcing contactsmounted on one of said terminals, a movable switch arm pivotally mountedon the other of said terminals and having a movable contact assemblagethereon comprising main, intermediate and arcing contacts forcooperating with the corresponding stationary contacts of the stationarycontact structure for establishing an arc, an arc chute structure havingarc-extinguishing means therein, said stationary contact structure andsaid co- 7 operating movable contact assemblage being compactly arrangedand disposed entirely within said arc chute so that any are or restrikewill occur within said are chute,-

and insulating means surrounding a portion of said movable switch armadjacent said are chute to' prevent the arc from striking said switcharm outside said are chute.

8. In a circuit breaker, a pair of terminals, a stationary contactstructure mounted on one of said terminals comprising stationary main,intermediate and arcing contacts, a movable switch member pivotallymounted on the other of said terminals, a flexible conductorelectrically connecting said movable switch arm to said other terminal,a movable contact assemblage mounted on said movable switch membercomprising movable main, intermediate and arcing contacts, said movablecontact assemblage cooperating with said stationary contact structure toestablish an arc, an arc chute structure having arc-extinguishing 8means therein, said stationary contact structure and said cooperatingmovable contact assemblage being arranged compactly and disposedentirely Within said are chute so that any arc or restrike of the arcwill occur within said are chute, and an insulating sleeve surrounding aportion of said movable switch member adjacent said arc chute.

References Cited in the file of this patent UNITED STATES PATENTS1,074,431 Hewlett Sept. 30, 1913 2,259,971 Cumming et al Oct. 21, 19412,462,283 Rathert Feb. 22, 1949 2,477,189 Lerstrup July 26, 19492,492,762 Palme Dec. 27, 1949 2,571,933 Olsson et al Oct. 16, 1951

